Magnetic Circuit Analysis / DRM Uniform Magnetic Field Circuit
Dipole ring magnets are used to imprint a uniaxial direction magnetic field over a wide space. They are primarily used in semiconductor manufacturing applications and in medical and other basic research fields. Compared to superconductors and normal conducting coils, there are maintenance free and have good uniformity and magnetic field directionality (skew angle). A DRM magnetic circuit comprises segment magnets laid out so that the magnetization direction changes 180° for one rotation and formed into a circle as in Figure (a).
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Figure (a) DRM magnetic circuits
The left side of Figure (b) is a sketch of a DRM magnetic circuit. The red cylindrical area that can be seen at the center of the circuit is called the evaluation space (space with uniform magnetic field). A normal DRM magnetic circuit is designed and manufactured so that the magnetic field in this space is uniform. The section that holds the magnets is the non-magnetic body.
As a result of optimizing the magnetic circuit based on magnetic field analysis, the contour diagram is as on the right of Figure (b). The red area in the analysis results is the area with a high magnetic field and the purple area has a low magnetic field. The contour level range is ±1%, which is extremely good uniformity. The skew angle is held to a mere 0.7 °.
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Figure (b) Magnetic field distribution of DRM uniform magnetic field circuit
